Many types of skin treatments have been developed which attempt to repair damaged skin. Typically, consumers and manufacturers evaluate these skin treatments on a subjective/objective basis based on whether the treatment relieves symptoms such as roughness, dryness, redness, or the discomfort of pain or itch. Some specific measures used to determine effectiveness are: feel (greasy/non-greasy), drying time, barrier effectiveness and duration, smell, efficacy of moisturization and the like. These features are determined by the lipids or hydrocarbons of the composition, other additives and the solvent in which they are provided.
Skin treatments typically come in the form of creams or lotions, which are emulsions of lipids and other components. Commercially successful skin treatments such as Vaseline(trademark) petroleum jelly still have recognized draw-backs, such as their greasy feel, and the long drying time required. This prevents users from quickly applying the Vaseline(trademark) and returning to other activities. These and other drawbacks affect existing skin treatments.
In recent years, it has been recognized that the permeability barrier of mammalian skin is found in unusual intercellular domains in the upper layers of the epidermis, and is composed mainly of three lipid classes: ceramide, cholesterol and free fatty acid. (see Kitson N, et al. A model membrane approach to the epidermal permeability barrier. Biochemistry. 1994;33:6707-15). To date no one has successfully applied this information to reconstitute this permeability barrier when it is lost. This is particularly relevant to humans who lose or damage this barrier either as the result of a pathological condition, or in the course of daily activities.
It is an object of the invention to provide a novel composition for use as a skin or hair treatment. It is also an object of the invention to take advantage of the phase transition properties of certain lipid formulations that result upon application to the skin, to provide an improved skin or hair treatment. It is a further object of this invention to provide formulations of therapeutic and bioactive agents in a treatment for use in topical skin-care applications.
The instant invention provides a composition which when topically applied to the skin of a mammal reduces trans-epidermal water-loss and provides an improved epidermal barrier. The composition comprises an aqueous dispersion of at least two lipids, preferably at least three lipids, in a non-crystalline phase lamellar array, preferably bilayer membranes in the form of liposomes. These lipids adopt a crystalline lamellar phase upon application to mammalian skin which resist washing with mild detergents and water.
In addition, the invention comprises a pharmaceutical preparation comprising a therapeutic compound in an aqueous formulation of at least two lipids in a non-crystalline phase lamellar array which adopt a crystalline lamellar phase upon application to mammalian skin and further comprising a therapeutic or bioactive agent.
The invention further comprises a method of recovering or otherwise improving a mammalian skin permeability barrier by administering to the skin or hair a composition of lipids comprising an aqueous formulation of at least two lipids in a non-crystalline phase lamellar array; and allowing said composition to dry, wherein said dried composition adopts a crystalline lamellar phase after said administering to the skin.
The perceived advantages of the invention are:
1. Provision of a permeability barrier in cases where the natural barrier has been depleted, damaged or requires improvement
2. Provision of a barrier that resists removal by detergent, solvent, or mechanical means.
3. Extended duration of efficacy.
4. Improved acceptability, particularly in feeling xe2x80x9cnon-greasyxe2x80x9d.
5. Can be a vehicle for a wide variety of active agents.
6. May allow reduced wastage of active agents.
7. May improve quality of skin or hair.